Problems with setting the focus of a control

Hi Guys,
I'm having an issue with setting the focus to the next textbox after a textbox_TextChanged event.
I should add that this works without any issues in IE9, it's just IE8 that's causing me grief (at the moment!). Firefox is fine too, but as a department, we only need to worry about IE.
Anyway, in IE8, the focus sometimes goes down to the next textbox (which is correct), sometimes goes to the textbox to it's right and then sometimes to the top corner textbox; so it really doesn't have a clue what it's doing!
The meta tag I'm using is the following:
<meta http-equiv="X-UA-Compatible" content="IE=edge" />


Here is the code that sets the tab index for all of the textboxes in a table- should go from row 1 col 1 to row 1 col 10 (for example) and then row 2 col 1 etc...
public HtmlTable SetTabIndex(HtmlTable table) { short focus = 1; i ...